They can be Charlie and in the past there have been issues when the fire brigade want to either reduce the heat of the fire (hose it down a bit) or spray buildings to cool them off. Plastic guttering and barge boards tend to warp or melt.

The councils do try to ensure the fires are not built near property and the size of the fire is appropriate to the space around it but it can be contentious at times, especially when the builders use lots, and I mean hundreds, of old tyres which produce tons of heat and smoke. They aren't supposed to but it happens year after year.